Ideas for code katas

[Fox]

On Monday we tried a new kata that I came up with based upon a real-world problem, that of implementing a (in this case simple) work-flow. In the past I've used:

• Algorithmic katas e.g. quicksort, bloom filters
• Game katas e.g. noughts and crosses, elementary cellular automata
  
• Domain katas e.g. shopping basket, work-flow

I'm wondering if people have some good ideas for new katas that will keep things interesting?

Thanks,

Fox

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